Detailed Description
[ grain-oriented Electrical Steel sheet and method for producing the same ]
The grain-oriented electrical steel sheet of the present invention is a grain-oriented electrical steel sheet comprising a steel sheet, a coating a containing a crystal disposed on the steel sheet, and a coating B containing a glass disposed on the coating a, wherein an element distribution in a direction from the coating B toward the steel sheet, which is obtained by radio frequency glow discharge emission spectroscopy, satisfies the following expressions (1) and (2).
0.35≤(tA/tFe/2)≤0.75…(1)
0.25≤(tA/2/tFe/2)≤1.00…(2)
Wherein, tAThe peak time, t, representing the distribution of the alkali metal elementA/2Half-peak time, t, representing distribution of alkali metal elementsFe/2Represents the half-peak time of the distribution of Fe.
The grain-oriented electrical steel sheet of the present invention has high tensile strength imparted to a steel sheet and excellent film adhesion. The film adhesion includes the adhesion between the film B and the film a and the adhesion between the film a and the steel sheet.
Hereinafter, the grain-oriented electrical steel sheet of the present invention will be described in more detail. First, the element distribution will be described, and then the respective configurations (steel sheet, coating a, and coating B) will be described. The following description is also applicable to a method for producing a grain-oriented electrical steel sheet of the present invention.
< distribution of elements >
The element distribution in the direction from the coating film B to the steel sheet (also referred to as "sheet thickness direction") was measured by a radio frequency glow discharge emission spectroscopy (rf-GD-OES) method.
Specifically, the measurement was performed using a Marcus type radio frequency glow discharge emission spectrometer "GD-Profiler 2" manufactured by horiba Ltd, using Ar 100% as a plasma gas, under conditions of a gas pressure of 600Pa, a radio frequency output of 35W, and a measurement interval of 0.1 sec/point.
In the graph of the element distribution, the horizontal axis represents the sputtering time (measurement time), and the vertical axis represents the emission intensity (intensity value) of the element. For example, please refer to fig. 1 and 2.
Fig. 1 shows an example of the element distribution measured for a grain-oriented electrical steel sheet of a comparative example. Fig. 2 shows an example of the element distribution measured for the grain-oriented electrical steel sheet of the present invention. Both fig. 1 and fig. 2 are graphs showing the distribution of Fe, Mg and Na.
When the element distributions in fig. 1 and 2 were measured, samples of grain-oriented electrical steel sheets were produced as follows.
First, a grain-oriented electrical steel sheet having a thickness of 0.23mm and subjected to finish annealing, which was produced by a known method, was cut into a size of 300mm (rolling direction) × 100mm (rolling perpendicular direction), and after removing an unreacted annealing separator, the cut pieces were N-cut at 800 ℃ for 2 hours2And performing stress relief annealing under the condition of atmosphere. A coating film A containing forsterite as a crystal is formed on the surface of a steel sheet.
Subsequently, slight acid washing was performed using a 5 mass% phosphoric acid aqueous solution. After slight pickling, the sample was set as untreated in the comparative example of FIG. 1. On the other hand, in the present invention shown in FIG. 2, the coating composition was immersed in a 10 mass% aqueous solution of NaOH at 25 ℃ for 5 seconds and then washed with water, whereby the content per unit area (both surfaces) of NaOH was 0.01g/m2。
Then, the magnesium phosphate aqueous solution (100 parts by mass in terms of solid content), colloidal silica (50 parts by mass in terms of solid content), and CrO were mixed3(15 parts by mass) the aqueous solution thus mixed was diluted with pure water to adjust the specific gravity to 1.20g/cc, thereby obtaining a coating liquid. The obtained coating liquid was applied by a roll coater in an amount of 10g/m after drying both sides2The coating is applied to both sides of the steel sheet with the coating film a.
The steel sheet with the coating film A coated with the coating liquid was charged into a drying furnace, dried at 300 ℃ for 1 minute, and then dried at 800 ℃ for 2 minutes under N2Sintering was performed under 100%. By firing, a coating B containing silico-phosphate glass as a vitreous material was formed on the coating a.
The samples of the grain-oriented electrical steel sheet (coating B/coating a/steel sheet) thus obtained were obtained.
half-Peak time t of distribution of FeFe/2》
When the distribution of Fe has a peak, the half-peak time t of the distribution of FeFe/2The time (time on the front surface side) of one-half of the intensity value representing the peak is set.
When the distribution of Fe does not have a peak, it is set as follows. First, sputtering is performed for a long time, and the sputtering reaches the steel sheet (steel base) sufficiently, waiting for the emission intensity of Fe to become a constant value. Then, the time at the outermost surface side (coating B side) of the half intensity value of the emission intensity (intensity value) of Fe that indicates a constant value is set as the half-peak time t of the distribution of FeFe/2。
Peak time t of distribution of alkali metal elementA》
The peak time t of the distribution of the alkali metal element (hereinafter sometimes referred to as "A")AThe peak time is set to the peak time when there is one peak, and the peak time of the highest peak is set to the peak time when there are a plurality of peaks.
half-Peak time t of distribution of alkali Metal elementA/2》
Half-peak time t of distribution of alkali metal elementA/2The time is set to one-half of the intensity value indicating the intensity value of the peak (the peak is the one peak when there is one peak, and the highest peak when there are a plurality of peaks). Further, let t be the half-peak time on the front surface side (coating film B side)A/2surLet the half-peak time on the steel plate side be tA/2met。tA/2Is composed of tA/2surAnd tA/2metBoth concepts.
Formula (1): t is not more than 0.35A/tFe/2)≤0.75》
For formula (1): t is not more than 0.35A/tFe/2) The specification is less than or equal to 0.75.
tA/tFe/2If the content is less than 0.35, the alkali metal element is not concentrated at the interface between the coating a and the coating B and is mainly contained only in the coating B, and the tension applied to the steel sheet is insufficient.
tA/tFe/2If the content is more than 0.75, the coating a is wetted with the alkali metal element and concentrated at the crystal interface, the grain boundary strength is reduced, and the adhesion between the coating a and the steel sheet is poor.
In contrast, if tA/tFe/20.35 or more and 0.75 or less, the alkali metal element is concentrated at the interface between the coating film a and the coating film B. In this case, the wettability of the interface between the coating a and the coating B is good, and the adhesion between the coating a and the coating B is excellent. In addition, a state in which a large amount of alkali metal element is contained in the coating film B is avoided, and the tensile force applied to the steel sheet is excellent. Further, the state of the coating a wetted with the alkali metal element is avoided, and the adhesion between the coating a and the steel sheet is excellent.
tA/tFe/2Preferably 0.40 or more and 0.75 or less.
Formula (2): t is not more than 0.25A/2/tFe/2)≤1.00》
P-formula (2): t is not more than 0.25A/2/tFe/2) The expression is less than or equal to 1.00.
As described above, tA/2Is composed of tA/2surAnd tA/2metBoth concepts. t is tA/2sur/tFe/2And tA/2met/tFe/2It is required to be 0.25 to 1.00.
tA/2sur/tFe/2If the content is less than 0.25 (i.e., the distribution of the alkali metal element is wide), it cannot be said that the alkali metal element is concentrated at the interface between the coating a and the coating B, and the alkali metal element is mainly contained only in the coating B, which has an effect of improving the adhesion, but the tension applied to the steel sheet is insufficient.
tA/2met/tFe/2If the amount exceeds 1.00, the coating a is impregnated with a large amount of alkali metal elements, and the alkali metal elements are concentrated at the crystal interface, resulting in a decrease in grain boundary strength and poor adhesion between the coating a and the steel sheet.
In contrast, if tA/2/tFe/2(i.e., t)A/2sur/tFe/2And tA/2met/tFe/2Both of them) is 0.25 or more and 1.00 or less, the alkali metal element is concentrated at the interface between the coating film a and the coating film B, as in the formula (1). Such asIn this case, the wettability of the interface between the coating a and the coating B is good, and the adhesion between the coating a and the coating B is excellent. In addition, a state in which a large amount of alkali metal element is contained in the coating film B is avoided, and the tensile force applied to the steel sheet is excellent. Further, the state of the coating a wetted with the alkali metal element is avoided, and the adhesion between the coating a and the steel sheet is excellent.
tA/2/tFe/2Preferably 0.30 or more and 0.90 or less.
Types of alkali Metal elements
Examples of the alkali metal element (i.e., the alkali metal element concentrated in the interface between the coating a and the coating B) include Li, Na, K, Rb, Cs, and Fr.
Among these, at least one selected from the group consisting of Li, Na, and K is preferable to Rb, Cs, and Fr for the reason of excellent price and availability, and at least one selected from the group consisting of Na and K is more preferable to Li for the reason of high tension applied to the steel sheet.
The method for adjusting the distribution of the alkali metal element will be described later.
Next, the respective configurations (steel sheet, coating a, and coating B) of the grain-oriented electrical steel sheet of the present invention will be described.
< Steel sheet >
The steel sheet is not particularly limited, and for example, from the viewpoint of magnetic properties, a steel slab to be a steel sheet is preferably: the steel contains, in mass%, C: 0.001-0.10%, Si: 1.0-5.0%, Mn: 0.01-1.0%, sol.Al: 0.003-0.050%, N: 0.001-0.020%, S: 0.001-0.05% and/or Se: 0.001 to 0.05%, and the balance of unavoidable impurities and Fe.
C is a component useful for the generation of gaussian-oriented crystal grains, and the C content is preferably 0.001 mass% or more in order to effectively exhibit this effect. On the other hand, when C is too large, decarburization defects may occur even by decarburization annealing, and therefore the C content is preferably 0.10 mass% or less.
Si is a component necessary for reducing the iron loss by increasing the electric resistance and stabilizing the BCC structure of iron so as to enable high-temperature heat treatment, and the Si content is preferably 1.0 mass% or more, and more preferably 2.0 mass% or more. On the other hand, when Si is too much, cold rolling may be difficult, and therefore the Si content is preferably 5.0 mass% or less.
Mn not only contributes effectively to improvement of hot shortness of steel, but also forms precipitates such as MnS and MnSe when S, Se is mixed, and functions as an inhibitor (inhibitor). From the viewpoint of sufficiently obtaining the effect, the Mn content is preferably 0.01 mass% or more. On the other hand, when Mn is too large, the grain size of precipitates such as MnSe may be coarsened and the effect as an inhibitor may be lost, and therefore the Mn content is preferably 1.0 mass% or less.
Al is a useful component that forms AlN in steel and acts as an inhibitor for dispersing the second phase. When the amount of Al is too small, the amount of precipitation may not be sufficiently secured. On the other hand, when Al is too large, AlN may be coarsely precipitated and lose its function as an inhibitor. Therefore, the sol.Al content is preferably 0.003 to 0.050% by mass.
Like Al, N is a component for forming AlN. When N is too small, precipitation of AlN may become insufficient. On the other hand, if N is too large, foaming may occur during heating of the billet. Therefore, the N content is preferably 0.001 to 0.020% by mass.
S and Se are combined with Mn and Cu to form MnSe, MnS and Cu2-xSe、Cu2-xS and the like as a useful component which functions as a suppressor for the dispersed second phase in the steel. When the amount of S and/or Se is too small, the addition effect may be insufficient, and when too large, the solid solution may be incomplete during heating of the slab or may cause defects on the surface of the product. Therefore, the content of S and/or Se is preferably 0.001 to 0.05 mass%.
The steel slab to be a steel sheet may further contain, in mass%, a metal selected from the group consisting of Cu: 0.01 to 0.2%, Ni: 0.01-0.5%, Cr: 0.01 to 0.5%, Sb: 0.01 to 0.1%, Sn: 0.01 to 0.5%, Mo: 0.01 to 0.5% and Bi: 0.001 to 0.1% of at least one element of the group. The magnetic properties can be further improved by adding an element having an effect as an auxiliary inhibitor. Examples of such an element include the above-mentioned elements. When any element does not satisfy the above content, the effect is hardly obtained. On the other hand, if the content exceeds the above range, appearance defects of the coating film and secondary recrystallization defects may easily occur. Therefore, the content is preferably within the above range.
The steel slab to be a steel sheet may further contain, in addition to the above components, in mass%, a component selected from the group consisting of: 0.001-0.01%, Ge: 0.001 to 0.1%, As: 0.005-0.1%, P: 0.005-0.1%, Te: 0.005-0.1%, Nb: 0.005-0.1%, Ti: 0.005-0.1%, and V: 0.005-0.1% of at least one element of the group. This further strengthens the suppression force, and can stably obtain a higher magnetic flux density.
The steel sheet is produced, for example, as follows.
First, the slab is hot-rolled to obtain a hot-rolled sheet. The hot-rolled sheet is annealed as necessary, and then subjected to one cold rolling or two or more cold rolling with intermediate annealing, to obtain a cold-rolled sheet having a final sheet thickness. A cold-rolled sheet is subjected to primary recrystallization annealing and decarburization annealing (usually, primary recrystallization annealing is also performed as decarburization annealing), and then, after an annealing separator is applied, final annealing is performed. Thus, a steel sheet (grain-oriented electrical steel sheet) having developed gaussian-oriented crystal grains (secondary recrystallized grains) was obtained. The production conditions may be those conventionally known, and are not particularly limited.
For example, when an annealing separator containing MgO as a main component is used, a forsterite-containing coating (forsterite coating) is formed on the surface of the obtained steel sheet.
For example, by using Al2O3An annealing separator, which is a main component, forms a cordierite-containing film (cordierite film) on the surface of the obtained steel sheet.
The forsterite film and the cordierite film correspond to a film a described later.
When these coatings are used as the coating a, a coating B described later can be formed as it is.
When these coatings are not used as the coating a, the coatings are removed by acid washing or the like, and then another coating a (for example, a nitride-containing coating a described later) is formed, followed by formation of a coating B described later.
A grain-oriented electrical steel sheet (steel sheet) may be produced without forming these coatings.
< coating A >
The coating a is a coating containing a crystal disposed on the steel sheet. The method for producing the coating a is not particularly limited, and examples of methods other than the above-described methods include CVD (Chemical Vapor Deposition), PVD (Physical Vapor Deposition), sol-gel method, and steel plate oxidation.
The crystalline material of the coating film a may be, for example, an oxide, and specific examples thereof may be at least one selected from the group consisting of forsterite and cordierite. The coating a containing forsterite as a crystalline oxide is the above-described forsterite coating. The coating film a containing cordierite as a crystalline oxide is the above-described cordierite coating film. The method for obtaining these coatings is as described above.
The crystal of the coating film a may be a nitride. As the nitride, a metal nitride can be cited. As the metal nitride, a metal nitride containing at least one metal selected from the group consisting of Ti, Al, and Cr is preferable, and at least one selected from the group consisting of titanium nitride (TiN), aluminum nitride (AlN), and chromium nitride (CrN) is more preferable.
The nitride-containing coating film a is formed by, for example, a CVD method or a PVD method.
The content of the crystalline substance in the coating a is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass.
The content of the crystalline substance in the coating film a can be measured by X-ray diffraction using a standard curve.
The coating a may be two or more layers.
The thickness of one surface of the coating A (the total thickness of the two or more layers) is not particularly limited, but is preferably 0.05 to 5.00. mu.m, and more preferably 0.10 to 3.00. mu.m.
< coating film B >
The coating B is a coating containing glass disposed on the coating a, and is a so-called insulating tension coating.
The glass material of the coating B includes, for example, a silicophosphate glass, and specific examples thereof include suitably a silicophosphate glass containing at least one metal element selected from the group consisting of Mg, Al, Ca, Ti, Nd, Mo, Cr, B, Ta, Cu, and Mn. From the viewpoint of recent environmental restrictions, it is more preferable that Cr is not contained.
The coating B may contain a crystal (except for the crystal contained in the coating a). The balance except vitreous is crystalline.
The content of the glass in the coating B is preferably 10 to 100 mass% because the coating adhesion between the coating a and the coating B may deteriorate when the content is less than 10 mass%.
Further, by making the vitreous material contain a crystal to form a crystallized glass, properties (for example, low thermal expansion property, high heat resistance, etc.) which cannot be obtained by the vitreous material alone can be provided. Therefore, the content of the glass substance in the coating film B is more preferably 30 to 90 mass%, and still more preferably 40 to 70 mass%.
When the method of forming the coating B is the method B1 or the method B2 described later, the content of the glass in the formed coating B is considered to be 10 mass% or more.
The method for forming the coating B is not particularly limited, and examples thereof include the following methods (method B1): the coating liquid is applied to the coating a, and then sintered to obtain a coating B. The sintering may be a planarization annealing that doubles as sintering.
The coating liquid preferably contains phosphoric acid and/or a phosphate salt and colloidal silica. Examples of the metal species of the phosphate include Mg, Al, Ca, Mn, Ni, and the like.
The coating liquid may further contain a metal compound. As the metal species of the metal compound, for example, at least one selected from the group consisting of Mg, Al, Ca, Ti, Nd, Mo, Cr, B, Ta, Cu, and Mn can be cited. B (boron) is treated as a metal.
The content of each component in the coating liquid is not particularly limited and may be set as appropriate.
When the coating liquid is used, the sintering temperature is, for example, 600 to 1000 ℃. The sintering time is, for example, 1 to 300 seconds. The sintering atmosphere is, for example, a nitrogen atmosphere.
The method for forming the coating film B may be the following method (method B2): the coating film B is obtained by applying the glass frit to the coating film a and then sintering the glass frit.
The glass frit contains PbO and SiO based on oxide2、B2O3BaO, ZnO, etc.
When the glass frit is used, the sintering temperature is, for example, 600 to 1200 ℃. The sintering time is, for example, 5 to 20 minutes. The sintering atmosphere is, for example, a nitrogen atmosphere.
The coating film B may be two or more layers.
The film thickness on one side of the coating B (the total thickness of each layer in the case of two or more layers) is preferably 1.0 to 6.0 μm, and more preferably 1.5 to 4.0 μm, from the viewpoint of obtaining good interlayer resistance and space factor.
The tension applied to the steel sheet by the coating B is, for example, 8MPa or more, preferably 10MPa or more, and more preferably 12MPa or more. By increasing the tension applied to the steel sheet, the iron loss can be reduced, or the noise when used in a transformer can be reduced.
< method for adjusting distribution of alkali Metal element >
The method for producing a grain-oriented electrical steel sheet of the present invention is a method including a step of obtaining a steel sheet with a coating a and a step of forming a coating B on the coating a of the steel sheet with the coating a.
In this case, the method for adjusting the distribution of the alkali metal element so as to satisfy the above formulae (1) and (2) is not particularly limited, and examples thereof include the following methods 1 to 3.
Method 1
The method 1 is as follows: before the coating B is formed, the steel sheet with the coating a is immersed in an aqueous solution of an alkali metal compound, and then washed with water and dried. At this time, the distribution of the alkali metal element is adjusted by adjusting the washing conditions such as the washing time.
The alkali metal compound is not particularly limited, and examples thereof include LiOH, NaOH, KOH and Li2SO4、Na2SO4、K2SO4、LiCl、NaCl、Na2HPO4、K2HPO4And the like.
In method 1, the content of the alkali metal compound in the aqueous solution in which the steel sheet with the coating a is immersed is preferably 1 mass% or more, more preferably 5 mass% or more, from the viewpoint of easily obtaining the content per unit area described later. On the other hand, the content is preferably 40% by mass or less, more preferably 30% by mass or less, for the reason that the amount of alkali metal compound removed by washing with water is not too large and is relatively economical.
In method 1, the temperature of the aqueous solution of the alkali metal compound to be immersed in the steel sheet with the coating a is preferably 10 ℃ or higher, more preferably 15 ℃ or higher, from the viewpoint of easily obtaining the content per unit area described later. On the other hand, from OH of alkali metal compounds-、SO4 2-、Cl-The temperature is preferably 80 ℃ or lower, more preferably 70 ℃ or lower, from the viewpoint that the coating A and the steel sheet are less likely to be corroded by the anions.
In method 1, the time (immersion time) for immersing the steel sheet with the coating film a in the aqueous solution of the alkali metal compound is not particularly limited, and is, for example, 1 to 60 seconds, preferably 5 to 30 seconds.
The content per unit area of the alkali metal compound in terms of alkali metal element in the steel sheet with the coating film A after drying is, for example, 1.0X 10 on both sides-6mol/m2From the viewpoint of better adhesion of the coating film, the above ratio is preferably 1.0 × 10- 5mol/m2The above.
The upper limit of the content per unit area is not particularly limited, and is, for example, 1.0X 10-2mol/m2The following.
The content per unit area of the alkali metal element of the alkali metal compound is determined from the change in mass of the steel sheet with the coating film a before and after the treatment (immersion in an aqueous solution of an alkali metal compound, washing with water, and drying). In addition, if a plurality of steel sheets with a coating film a having different contents of alkali metal elements per unit area are prepared in advance and used as a calibration plate and a calibration curve is prepared from the fluorescent X-ray count of the alkali metal element, the content per unit area of the alkali metal compound in terms of the alkali metal element can be easily measured by the fluorescent X-ray.
In method 1, after drying, a coating liquid or the like is applied to the coating film a and sintered to form a coating film B. In this case, by changing the sintering conditions such as the sintering time of the coating film B, the diffusion of the alkali metal element can be controlled, and the distribution of the alkali metal element can be adjusted.
Method 2
The method 2 is as follows: the coating liquid is applied and sintered a plurality of times to form a multilayer coating film B on the coating film a. The colloidal silica used in the coating liquid may contain an alkali metal element such as Na. In the method 2, for example, the amount of the alkali metal element of the colloidal silica used in the first layer coating film B is made larger than the amount of the alkali metal element of the colloidal silica used in the second layer coating film B. Thereby, the distribution of the alkali metal element is adjusted so as to satisfy the above formulas (1) and (2).
Method 3
The method 3 is as follows: the coating and sintering of the frit are performed a plurality of times to form a multilayer coating B on the coating a. In method 3, an alkali metal compound such as KOH or NaOH is added to the glass frit used for the first layer coating film B. Thereby, the distribution of the alkali metal element is adjusted so as to satisfy the above formulas (1) and (2).
Examples
The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples.
[ test example 1]
< production of oriented Electrical Steel sheet >
A sample of a grain-oriented electrical steel sheet having a coating a and a coating B in this order on the steel sheet was prepared as described below.
First, a composition containing Si: 3.3%, C: 0.06%, Mn: 0.08%, S: 0.001%, Al: 0.015%, N: 0.006%, Cu: 0.05% and Sb: 0.01% of silicon steel billet.
The silicon slab was heated at 1100 ℃ for 30 minutes and then hot-rolled to obtain a hot-rolled sheet having a thickness of 2.2 mm. The obtained hot-rolled sheet was annealed at 1000 ℃ for 1 minute, and then cold-rolled to obtain a cold-rolled sheet coil having a final sheet thickness of 0.27 mm. A cold-rolled sheet sample having a dimension of 100mm (rolling direction in the right angle direction) × 400mm (rolling direction) was cut from the center of the obtained cold-rolled sheet coil. The cut cold-rolled sheet sample was heated in the laboratory at a heating rate of 20 ℃/sec from room temperature to 820 ℃ and subjected to primary recrystallization annealing at 820 ℃ for 60 seconds in a humid atmosphere. Next, 10 parts by mass of TiO was mixed with 100 parts by mass of MgO2The annealing separator thus obtained was applied to the surface of a cold-rolled sheet sample subjected to primary recrystallization annealing in the form of an aqueous slurry, and dried. The dried cold rolled sheet samples were subjected to the following final annealing: the temperature is raised between 300 ℃ and 800 ℃ for 100 hours, then raised to 1200 ℃ at a rate of 50 ℃/hour, and annealed at 1200 ℃ for 5 hours. Thereby, a coating a containing forsterite as a crystal (forsterite coating) was formed, and a steel sheet with the coating a was obtained. The film thickness of the film A (forsterite film) was 1.20. mu.m. The content of the crystalline substance in the coating film a is 80 mass% or more.
The obtained steel sheet with the coating film a was immersed in a 5 mass% aqueous solution of an alkali metal compound described in table 1 below at 25 ℃ for 10 seconds. Then, the film was washed with pure water and dried. At this time, the content per unit area (both surfaces) of the alkali metal compound after drying in terms of the alkali metal element is adjusted by adjusting the degree of washing with water. The content per unit area was measured by the method described above.
Next, a magnesium phosphate (Mg (PO)) was prepared3)2Converted to 30 mol%), colloidal silica (in terms of SiO)2Converted to 60 mol%) and CrO3(10 mol%) of a silicon phosphate-based insulating tension coating liquid. The prepared coating liquid was applied to the coating film a and sintered at 850 ℃. Thereby, a coating containing a silicophosphate glass as a glass substance was formed on the coating AAnd (B) a film.
In this case, the sintering time (unit: s (sec)) shown in Table 1 below was set.
As the colloidal silica, an acidic type colloidal silica "SNOWTEX-O" (Na content: 0.03 mass%) manufactured by Nissan chemical Co., Ltd was used.
The coating amount of the coating liquid was set to 10g/m on both sides2。
The film thickness of the coating B was 2.5 μm on one side.
< measurement of element distribution >
The distribution of elements in the thickness direction of the produced samples of the grain-oriented electrical steel sheet was measured under the above conditions using "GD-Profiler 2" manufactured by horiba Ltd. Determining half-peak time t of Fe distribution from the measurement resultFe/2And the peak time t of the distribution of the alkali metal elements (A: Li, Na, K)AAnd half peak time tA/2(tA/2sur、tA/2met). Then, t is obtainedA/tFe/2、tA/2sur/tFe/2And tA/2met/tFe/2. The results are shown in table 1 below.
< evaluation >
The samples of the grain-oriented electrical steel sheet thus produced were evaluated as follows. The results are shown in table 1 below.
Width of peeling of coating film
The produced sample of the grain-oriented electrical steel sheet was subjected to shearing processing in the sheet thickness direction using a shear. Then, the processed end was observed with a metal microscope, and the distance (distance from the processed end surface) at which the coating (at least one of the coatings A and B) peeled off from the processed end was measured and used as the coating peeling width (unit: mm) of the processed end.
The smaller the peeling width of the coating film, the more excellent the adhesion of the coating film, and the peeling width of the coating film in practical use is preferably less than 3.0 mm.
Diameter of curved exfoliation
The produced sample of grain-oriented electrical steel sheet was stress-relieved and annealed at 800 ℃ for 3 hours in a nitrogen atmosphere. Then, the sample was wound on a plurality of round bars having different diameters in 10mm units, and the minimum diameter (bend peeling diameter) at which peeling and cracking did not occur in the coating (at least either one of the coatings a and B) was determined. The smaller the bend peeling diameter (unit: mm), the more excellent the adhesion of the coating film, and the bend peeling diameter is preferably less than 40mm in practical use.
(imparting tension)
First, a corrosion-resistant tape is attached to one surface (entire surface) of a sample of a grain-oriented electrical steel sheet to be produced. Then, the sample to which the corrosion-resistant tape was attached was immersed in a 25 mass% NaOH aqueous solution at 110 ℃ for about 10 minutes, thereby removing the coating film B on the surface of the side to which the corrosion-resistant tape was not attached. The sample was warped due to the removal of the coating B on one side. The corrosion resistant tape was removed and the radius of curvature of the specimen was measured. The tensile force (unit: MPa) applied to the steel sheet by the coating B was determined from the measured curvature radius.
The applied tension is preferably 8.0MPa or more.
As shown in Table 1 above, it is found that the composition satisfies 0.35. ltoreq. tA/tFe/2) Not more than 0.75 and not more than 0.25 (t)A/2/tFe/2) When the thickness is 1.00 or less, the film peeling width and the bending peeling diameter are small, the film adhesion is excellent, and the tensile force applied to the steel sheet is high.
It is also found that the content per unit area (both surfaces) of the alkali metal compound in terms of the alkali metal element is 1.0X 10- 5mol/m2In the above case, the peeling width of the coating is 1.0mm or less, and the coating adhesion is further improved.
On the other hand, the value of (t) is not satisfiedA/tFe/2) No.2 of 0.75 or less had a large peeling width and a large peeling diameter at bending, and the adhesiveness of the coating was poor.
For values not satisfying 0.35 ≦ (t)A/tFe/2) And (t) is not less than 0.25A/2sur/tFe/2) No.10 toIn other words, the tension applied to the steel sheet is insufficient.
For not satisfying (t)A/2/tFe/2) No.12 No. 1.00 or less had a large peeling width and a large peeling diameter at bending, and the adhesiveness of the coating was poor.
For values not satisfying 0.25 ≦ (t)A/2sur/tFe/2) No.14, 17 and 23, the tension applied to the steel sheet was insufficient.
[ test example 2]
< production of oriented Electrical Steel sheet >
A sample of a grain-oriented electrical steel sheet having a coating a and a coating B in this order on the steel sheet was prepared as described below.
First, a steel sheet with a coating a (forsterite coating) was obtained in the same manner as in test example 1.
Next, a coating liquid containing phosphoric acid, colloidal silica and a metal compound is prepared. The content of phosphoric acid is expressed as P2O5The conversion was set to 0.5 mol/L. The content of colloidal silica is SiO2The conversion was set to 1.5 mol/L. The content of the metal compound was set to the content (unit: mol/L) shown in the following Table 2 in terms of metal oxide.
The prepared coating liquid was applied to the surface of the obtained steel sheet with the coating film a, and sintering was performed. Coating and sintering were performed twice. Thereby, two layers of the coating film B containing silico-phosphate glass as a glass substance are formed on the coating film a.
As the colloidal silica used as the coating liquid, colloidal silica "AT-300" (Na content: 0.55 mass%) manufactured by ADEKA was used for the first layer coating film B, and colloidal silica "AT-20N" (Na content: 0.03 mass%) manufactured by ADEKA was used for the second layer coating film B.
The sintering conditions for the coating film B were set to 900 ℃ for 30 seconds and a nitrogen atmosphere for both the first layer and the second layer.
The film thickness (unit: μm) of the coating film B was set as shown in Table 2 below. The film thickness was evaluated by cross-sectional SEM observation.
< measurement of element distribution >
The half-peak time t of the distribution of Fe was determined for the prepared sample of grain-oriented electrical steel sheet in the same manner as in test example 1Fe/2And the peak time t of the distribution of the alkali metal element (Na)AAnd half peak time tA/2(tA/2sur、tA/2met). Then, t is obtainedA/tFe/2、tA/2sur/tFe/2And tA/2met/tFe/2. The results are shown in table 2 below.
< evaluation >
The film peeling width, the bend peeling diameter, and the applied tension were determined for the prepared samples of grain-oriented electrical steel sheets in the same manner as in test example 1. The results are shown in table 2 below.
Further, the interlayer resistance and space factor of the prepared sample of the grain-oriented electrical steel sheet were measured in accordance with JIS C2550. The interlayer resistance was evaluated by a current value (franklin current value). The results are shown in table 2 below.
As shown in Table 2 above, it is found that the composition satisfies 0.35. ltoreq. tA/tFe/2) Not more than 0.75 and not more than 0.25 (t)A/2/tFe/2) When the thickness is 1.00 or less, the film peeling width and the bending peeling diameter are small, the film adhesion is excellent, and the tensile force applied to the steel sheet is high.
The coating B was found to tend to further increase the tensile force applied to the steel sheet as the film thickness increased.
On the other hand, the value of (t) is not satisfiedA/tFe/2) No.1 and No. 11 of 0.75 or less showed poor adhesion of the coating film.
For values not satisfying 0.35 ≦ (t)A/tFe/2) And (t) is not less than 0.25A/2sur/tFe/2) Nos. 16 and 20 are insufficient in tension applied to the steel sheet.
[ test example 3]
< production of oriented Electrical Steel sheet >
A sample of a grain-oriented electrical steel sheet having a coating a and a coating B in this order on the steel sheet was prepared as described below.
First, a composition containing Si: 3.3%, C: 0.06%, Mn: 0.08%, S: 0.001%, Al: 0.015%, N: 0.006%, Cu: 0.05% and Sb: 0.01% of silicon steel billet.
The silicon slab was heated at 1100 ℃ for 30 minutes and then hot-rolled to obtain a hot-rolled sheet having a thickness of 2.2 mm. The obtained hot-rolled sheet was annealed at 1000 ℃ for 1 minute, and then cold-rolled to obtain a cold-rolled sheet having a final thickness of 0.23 mm. Subsequently, the cold-rolled sheet was heated from room temperature to 820 ℃ at a heating rate of 20 ℃/sec, and subjected to recrystallization annealing once at 820 ℃ for 60 seconds in a humid atmosphere. Next, 150 parts by mass of Al was mixed with 50 parts by mass of MgO2O3And 1 part by mass of Na2B4O7·10H2The annealing separator made of O is applied to the surface of the cold-rolled sheet subjected to the primary recrystallization annealing after being made into an aqueous slurry, and dried. The dried cold-rolled sheet was subjected to the following final annealing: the temperature is raised between 300 ℃ and 800 ℃ for 100 hours, then raised to 1200 ℃ at 50 ℃/hour, and annealed at 1200 ℃ for 5 hours. Thus, a cordierite (2 MgO.2Al) -containing alloy was obtained2O3·5SiO2) A crystalline steel sheet (coil) with a coating a. A sample having a dimension of 100mm (rolling direction perpendicular to the rolling direction) × 400mm (rolling direction) was cut from the center of the coil stock thus obtained.
Some of the samples were stripped of the coating a (cordierite coating) using a mixed acid of sulfuric acid and hydrofluoric acid, and a coating a (nitride coating) containing a nitride shown in table 3 below as a crystal was formed by a PVD method.
The film thickness (unit: μm) of the coating A is shown in Table 3 below.
The content of the crystalline substance in the coating film a is 80 mass% or more.
Next, a glass frit manufactured by asahi glass company shown in table 3 below was applied to the surface of the steel sheet with the coating a, and was sintered to form a coating B. Since the glass frit had a large particle size, it was pulverized by a ball mill and used after adjusting the particle size to an average particle size of 1.0. mu.m.
Coating and sintering were performed twice to form two layers of coating film B. To form the first layer coating B, 0.2 mass% KOH was added to the frit.
The sintering conditions for the coating film B were set to 1000 ℃ for 10 minutes and a nitrogen atmosphere for both the first layer and the second layer.
The film thickness (unit: μm) of the coating film B was set as shown in Table 3 below. The film thickness was evaluated by cross-sectional SEM observation.
< measurement of element distribution >
The half-peak time t of the distribution of Fe was determined for the prepared sample of grain-oriented electrical steel sheet in the same manner as in test example 1Fe/2And the peak time t of the distribution of the alkali metal element (K)AAnd half peak time tA/2(tA/2sur、tA/2met). Then, t is obtainedA/tFe/2、tA/2sur/tFe/2And tA/2met/tFe/2. The results are shown in table 3 below.
< evaluation >
The film peeling width, the bend peeling diameter, and the applied tension were determined for the prepared samples of grain-oriented electrical steel sheets in the same manner as in test example 1. In addition, the interlayer resistance (franklin current value) and the space factor were obtained in the same manner as in test example 2. The results are shown in table 3 below.
As shown in Table 3 above, it is found that the composition satisfies 0.35. ltoreq. tA/tFe/2) Not more than 0.75 and not more than 0.25 (t)A/2/tFe/2) When the thickness is 1.00 or less, the film peeling width and the bending peeling diameter are small, the film adhesion is excellent, and the tensile force applied to the steel sheet is high.
The coating B was found to tend to further increase the tensile force applied to the steel sheet as the film thickness increased.
On the other hand, the value of (t) is not satisfiedA/2/tFe/2) No.2 of 1.00 or less was inferior in film adhesion.
For values not satisfying 0.35 ≦ (t)A/tFe/2) And (t) is not less than 0.25A/2sur/tFe/2) In Nos. 3, 8, 9 and 10, which are at least any one of them, the tension applied to the steel sheet is insufficient.
For not satisfying (t)A/tFe/2) No.6 of 0.75 or less had a large peeling width and a large peeling diameter at bending, and the adhesiveness of the coating was poor.